Longer episodes associated with ablation failure
NIEUWEGEIN, THE NETHERLANDS. It is well established that achieving a successful outcome of catheter ablation procedures for persistent and permanent atrial fibrillation (AF) is significantly more difficult than in the case of paroxysmal (intermittent) AF. There is also substantial evidence that a left atrial parasternal diameter greater than 55 mm (5.5 cm) is associated with a poorer outcome. Now a group of Dutch electrophysiologists reports that pre-procedure AF burden, more specifically the longest episode duration, is a strong predictor of outcome.

Their study involved 120 patients with symptomatic paroxysmal AF, but no significant structural heart disease (lone AF). All patients underwent a pulmonary vein isolation (PVI) procedure with a ring-shaped, multielectrode ablation catheter using alternating unipolar- and bipolar-phased radiofrequency energy. Patients were kept on antiarrhythmics during a 3-month blanking period and were then followed up at 6, 12, 18, and 24 months following the procedure. Follow-up included standard ECGs, 2-day and 7-day Holter monitoring at follow-up appointments and when patients reported symptomatic AF.

At the one-year follow-up, 66 patients (55%) were off antiarrhythmics and free of any atrial arrhythmia (AF, atrial flutter and tachycardia) after a single procedure, while another 10 (8%) were arrhythmia-free with the aid of amiodarone or Class I antiarrhythmics (propafenone, flecainide). At the 2-year follow-up, 49% were free of arrhythmia without the aid of drugs after a single procedure.

The researchers observed that longer duration of AF (years), longer duration of episodes (mean), and longer duration of the longest episode were all associated with poorer outcome. The average number of episodes per month in the group was 19 and, oddly enough, more frequent episodes prior to the procedure were associated with a greater chance of success. However, after multivariable analysis, the only pre-procedural variable predicting outcome was the duration of the longest episode.

In the successful group, the average duration of the longest episode was 33 hours as compared to 48 hours in the unsuccessful group. The only procedural variable predicting outcome was the need for electrical cardioversion during the procedure. Only 10% of the members of the successful group required cardioversion as compared to 36% in the unsuccessful group.
Mulder, AAW, et al. Freedom from paroxysmal atrial fibrillation after successful pulmonary vein isolation with pulmonary vein ablation catheter-phased radiofrequency energy. Europace, Vol. 14, 2012, pp. 818-25

Editor's comment: The findings of this study confirm that a single PVI without additional lesions is not adequate to deal with AF involving long-duration episodes. This, in reality, means that a circumferential, anatomically-guided PVI is less likely to be successful than a segmental, electrophysiologically-guided procedure (Haissaguerre/Natale protocol) when it comes to dealing with cases involving long-duration episodes. It also means that afibbers who are contemplating having a catheter ablation procedure should do so before their episodes become day-long. In my own case, when asked by Prof. Pierre Jais in Bordeaux whether I ever had experienced episodes lasting longer than 24 hours, my answer was yes. He remarked that in this case a standard PVI would not do the job, and that he would have to go "hunting" for offending foci on the left atrial wall and other "usual suspects".